Cancers are the commonest cause for death among all of the causes for death. The therapies therefor are mainly surgical treatment in combination with radiotherapy and chemotherapy. In spite of the developments of new surgical methods and discovery of new anti-cancer agents in recent years, treatment results of cancers are not improved very much at present except for some cancers.
In recent years, by virtue of the development in molecular biology and cancer immunology, cancer antigens recognized by cytotoxic T cells reactive with cancers, as well as the genes encoding the cancer antigens, were identified, and expectations for antigen-specific immunotherapies have been raised (see Non-patent Literature 1). In 1991 Boon et al of Ludwig Institute in Belgium isolated human melanoma antigen MAGE 1 recognized by CD8-positive T cells by a cDNA-expression cloning method using an autologous cancer cell line and cancer-reactive T cells (see Non-patent Literature 2). After the report by Boon, antigens recognized by CD8-positive T cells, such as tyrosinase (see Non-patent Literature 3), MART1/MelanA (see Non-patent Literature 4) and gp100 (see Non-patent Literature 5) have been isolated.
In immunotherapy, to reduce side effects, it is desired that the protein recognized as the antigen be one which exists in a small amount in normal cells and exists in an excess amount in cancer cells. Further, it is desired that the antigen protein contain, in addition to the peptide region which can induce antigen-specific cytotoxic T cells which directly attack the tumor expressing the antigen, a peptide region which can induce antigen-specific helper T cells that aid the activity of the cytotoxic T cells.
Recently, the possibility that YKL-40 may be used as a tumor marker in serum associated with human malignant brain tumor was suggested. It has been reported that this protein is excessively expressed in most of human malignant brain tumors and is not substantially expressed in normal brain tissues (see Non-patent Literature 6).    Non-patent Literature 1: Tsuyoshi AKIYOSHI, “Japanese Journal of Cancer and Chemotherapy”, 1997, vol. 24, p 551-519    Non-patent Literature 2: Bruggen P. et al., Science, 254: 1643-1647 (1991)    Non-patent Literature 3: Robbins P. F. et al., Cancer Res., 54: 3124-3126 (1994)    Non-patent Literature 4: Kawakami Y. et al., Proc. Natl. Acad. Sci. USA, 91(9): 3515-3519 (1994)    Non-patent Literature 5: Kawakami Y. et al., Proc. Natl. Acad. Sci. USA, 91: 6458-6462 (1994)    Non-patent Literature 6: Meena K. et al., Cancer Res., 62: 4364-4368 (2002)